Three people were arrested — one of them born in Australia — after an active shooter situation led to “significant” fatalities at the mosques during Friday prayers. Police said a fourth person was arrested Friday but that was “not related to these events.”

As soon as the news of the attacks broke, social media was flooded with condolences and people sending sympathies to New Zealand.

First and foremost, the prime minister of the country, Jacinda Ardern, made an emotional statement after the shootings, calling Friday “one of New Zealand’s darkest days.” She reiterated her message on Twitter.

What has happened in Christchurch is an extraordinary act of unprecedented violence. It has no place in New Zealand. Many of those affected will be members of our migrant communities – New Zealand is their home – they are us.

U.S. President Donald Trump posted a tweet condemning the “horrible massacre,” as did former leader Barack Obama.

My warmest sympathy and best wishes goes out to the people of New Zealand after the horrible massacre in the Mosques. 49 innocent people have so senselessly died, with so many more seriously injured. The U.S. stands by New Zealand for anything we can do. God bless all!

Celebrities of all stripes expressed shock and dismay as the events unfolded in Christchurch.

40 dead in NZ.Senseless, pointless, cruel deaths.My heart breaks for all the families involved, and for the beautiful people of New Zealand to whose hearts this pain will attach, for a long time. Kia Kaha.

My heart is broken. My country is weeping and so am I. I am dying knowing that this kind of hatred can happen in my homeland. All my love goes out to Christchurch, the victims, the families, the Muslim community, and all who have chosen our islands as their home. This is not us.

Horrified by the news of the mass shootings in two mosques in Christchurch, New Zealand. Hate knows no boundaries, especially when so heavily armed. Thinking of the shattered lives and communities, where hundreds had gathered for Friday prayers.

To the Muslim community— my heart is broken by the horror & loss in New Zealand. We are with you, we see you, and we will fight white supremacy and islamaphobia until we are all free of fear. #ChristchurchMosque

Prince William and Kate Middleton released a statement condemning the attacks. The Queen and Prince Philip also shared a message saying, “Prince Philip and I send our condolences to the families and friends of those who have lost their lives.”